<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML><HEAD> <META content="text/html; charset=windows-1252" = http-equiv=Content-Type> <META content="MSHTML 5.00.3019.2500" name=GENERATOR> <STYLE></STYLE> </HEAD> <BODY bgColor=#ffffff> <DIV><FONT size=2>Hello Terry,</FONT></DIV> <DIV> </DIV> <DIV><FONT size=2>The switch in our Humidistat has a synthetic polymer = band.  You can see it if you look through the vent holes on the = side of the Humidistat.  It will either be a clear polymer band or a white = woven polymer band.</FONT></DIV> <DIV><FONT size=2></FONT> </DIV> <DIV><FONT size=2>As moisture flows into the Humidistat the = band absorbs moisture and swells.  Eventually it swells enough to trigger a = mechanical switch which energizes the Dehumidifier outlet and shuts off the = Humidifier outlet.  Then drier air enters the Humidistat and the band begins = to shrink.  Eventually it shrinks enough to trigger a second = mechanical switching action which causes the Humidifier outlet to be energized and = the Dehumidifier outlet to be shut off.</FONT></DIV> <DIV> </DIV> <DIV><FONT size=2>In our humidity controlled test rooms the cycle = generally takes 3-4 hours with the Humidifier being on two thirds of the = time and the Dehumidifier being on a third of the time.  Say we have a = system installed in a vertical piano and we have a backside cover on the instrument.  A typical calibration for the Humidistat would be a = lower set point of 39% relative humidity and an upper set point of 45%.  If = we place a good hygrometer probe on the Humidistat and record the readings = during the cycling we can see a range of 35% to 65% relative = humidity.  So we can get up to 20% "overshoot" on humidification and a few percent = on "dehumidification".  Now after cycling has = been established we bring the test room relative humidity up to 70% and hold it there for = several weeks.  The soundboard stabilizes after a few days at an = equilibrium moisture content of 8.0% and then remains there +/- .1%.  = Then we lower the relative humidity in the test room to 20% and again hold it = there for a few weeks.  The equilibrium moisture content of the soundboard restabilizes at 7.2% and then remains there +/- .1%.  Then we = conduct the test again, but without a Climate Control System.  At 70% = relative humidity in the room the soundboard stabilizes at 10.8% equilibrium = moisture content.  At 20% relative humidity the sounboard stabilizes at 5.0% = equilibrium moisture content.  So the System reduces the = differential from almost 6% to 0.8%.  With a Backside Vertical System or a Grand = System with an undercover we can get down to a differential of 0.2%.  My = point is that even though the piano is seeing a controlled repeatable cycle of = relative humidity which is larger than one might expect, the soundboard = equilibrates and provides pitch stability to the instrument.</FONT></DIV> <DIV> </DIV> <DIV><FONT size=2>Electronic sensors measure relative humidity by = evaluating changes in resistance or capacitance in the air.  = Capacitor based systems are generally more accurate and more = expensive.  All electronic sensors react within a few minutes to a change in relative humidity.  The least expensive equilibrate within 30 minutes and = these are what you find in the inexpensive hygrometers.  Very expensive ones equilibrate very quickly.  While they are called electronic sensors = they really are in a sense measuring electrochemical events.  The = responsive of the sensors deteriorates with time, as I understand it, due to films = building on the sensor points resulting in a variable response to measuring the electrochemical event.  Thus they drift over time, so they = require replacement or recalibration.  The very expensive hygrometers we = use are not immune to this.  We have to return them to the factory for = recailibration annually.  What we are looking for at Dampp-Chaser = is an affordable electronic sensor that has minimal drift and a fast = response.  So far we haven't found it.</FONT></DIV> <DIV><FONT size=2></FONT> </DIV> <DIV><FONT size=2>I hope this helps.</FONT></DIV> <DIV> </DIV> <DIV><FONT size=2>Roger</FONT></DIV> <DIV> </DIV> <DIV><FONT size=2>ps - Terry, I am copying some of my staff on this as = Tammy and Mitch help me with technical customer service.  I hope you don't mind.</FONT></DIV> <BLOCKQUOTE style="BORDER-LEFT: #000000 2px solid; MARGIN-LEFT: 5px; MARGIN-RIGHT: = 0px; PADDING-LEFT: 5px; PADDING-RIGHT: 0px"> <DIV style="FONT: 10pt arial">----- Original Message ----- </DIV> <DIV style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: = black"><B>From:</B> <A href="mailto:mfarrel2@tampabay.rr.com" title=mfarrel2@tampabay.rr.com>Farrell</A> </DIV> <DIV style="FONT: 10pt arial"><B>To:</B> <A href="mailto:roger@dampp-chaser.com" title=roger@dampp-chaser.com>roger@dampp-chaser.com</A> </DIV> <DIV style="FONT: 10pt arial"><B>Sent:</B> Tuesday, January 16, 2001 = 8:36 PM</DIV> <DIV style="FONT: 10pt arial"><B>Subject:</B> Re: Climate Control Promotion</DIV> <DIV><BR></DIV> <DIV>Thank you Roger for your very informative response. You stated = your position well, and I think I have a much better feel for the role = these inexpensive hygrometers should be allowed to play.</DIV> <DIV> </DIV> <DIV>However, having a bit of a background in wood technology, I = really try to thoroughly understand climate control on pianos. You wrote of = humidistat "overshoot". I do not understand what it is you are referring to. See = below -</DIV> <DIV> </DIV> <DIV>"The sensing band in the Humidistat is slow to respond to a = rapid increase in humidity, and one observes "overshoot" where = higher than expected relative humidity levels are recorded by a hygrometer placed = in the vicinity of the Humidistat."</DIV> <DIV> </DIV> <DIV>"We experiment with electronic sensors that respond quickly to = avoid the "overshoot"."</DIV> <DIV> </DIV> <DIV>Could you please expand on this a bit to clarify?</DIV> <DIV> </DIV> <DIV>Additionally, or specifically, I am curious as to how fast do the = Humidistats respond. Is there anything you can say about that without Fed-Exing a 120 page report to me (I realize a good explanation might = require just that)?</DIV> <DIV> </DIV> <DIV>Thanks again for your input. I really appreciate it. If you think = your response would be of interest to the pianotec list, please post it = there - I would think it might.</DIV> <DIV> </DIV> <DIV>Terry Farrell<BR>Piano Tuning & Service<BR>Tampa, = Florida<BR><A = href="mailto:mfarrel2@tampabay.rr.com">mfarrel2@tampabay.rr.com</A></DI= V> <BLOCKQUOTE style="BORDER-LEFT: #000000 2px solid; MARGIN-LEFT: 5px; = MARGIN-RIGHT: 0px; PADDING-LEFT: 5px; PADDING-RIGHT: 0px"> <DIV style="FONT: 10pt arial">----- Original Message ----- </DIV> <DIV style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: = black"><B>From:</B> <A href="mailto:roger@dampp-chaser.com" = title=roger@dampp-chaser.com>Roger Wheelock</A> </DIV> <DIV style="FONT: 10pt arial"><B>To:</B> <A = href="mailto:pianotech@ptg.org" title=pianotech@ptg.org>pianotech@ptg.org</A> </DIV> <DIV style="FONT: 10pt arial"><B>Cc:</B> <A href="mailto:gayle@dampp-chaser.com" = title=gayle@dampp-chaser.com>Gayle Mair</A> ; <A href="mailto:mitchell_smith@dampp-chaser.com" = title=mitchell_smith@dampp-chaser.com>mitchell_smith@dampp-chaser.com</= A> ; <A href="mailto:tammy_bradley@dampp-chaser.com" = title=tammy_bradley@dampp-chaser.com>tammy_bradley@dampp-chaser.com</A>= </DIV> <DIV style="FONT: 10pt arial"><B>Sent:</B> Tuesday, January 16, = 2001 4:53 PM</DIV> <DIV style="FONT: 10pt arial"><B>Subject:</B> Re: Climate Control Promotion</DIV> <DIV><BR></DIV> <DIV><FONT size=2>Dear List,</FONT></DIV> <DIV> </DIV> <DIV><FONT size=2>I offer the following in hopes of shedding some = light on relative humidity readings measured with inexpensive digital = hygrometers inside a piano when a Dampp-Chaser Climate Control System is operating.  I will use the hygrometer we distribute as an example.  Please note that we only distribute this hygrometer = as a tool to use in showing a piano owner the extremes of relative humidity he = or she might experience in the home.  We have never promoted it as a = tool for technical or scientific studies.  In our testing we use = hygrometers that range in cost from approximately $500 to $1500.  We = believe that one needs to invest over $100 to get a reasonable tool to use in = testing System performance.</FONT></DIV> <DIV><FONT size=2></FONT> </DIV> <DIV><FONT size=2>We have switched hygrometer manufacturers and do = provide a slightly better hygrometer than we initially distributed.  But even these are only moderately accurate, reasonably precise = and the sensor will drift significantly with time.  (This is simply the = nature of the inexpensive electronic sensor in these instruments.)  So = kindly understand our intention was to provide a tool where you could show = a piano owner a 40-50% relative humidity swing had occurred when the = hygrometer was left in their home for a period of time.</FONT></DIV> <DIV> </DIV> <DIV><FONT size=2>The other source of some confusion is in how the = Climate Control System operates.  The Humidistat contains an = electromechanical switch.  We measure the calibration of each switch in one of = our humidity controlled test rooms.  Here we bring the humidity up = to about 65% and down to about 30% very slowly over a 20-hour period.  = Computers record the upper and lower set point for each switch and our regular = Humidistats now have a six percent range with the average of the two = set points falling between 42% and 44% relative humidity.</FONT></DIV> <DIV> </DIV> <DIV><FONT size=2>When a Climate Control System is = functioning within the piano the relative humidity rises and falls much faster than the twenty hours of controlled humidity change the = switch experienced in our calibration test room.  The sensing band in = the Humidistat is slow to respond to a rapid increase in humidity, = and one observes "overshoot" where higher than expected = relative humidity levels are recorded by a hygrometer placed in the vicinity = of the Humidistat.  We observe these in our product = development humidity controlled test rooms.  Here, however, we are also measuring = soundboard equilibrium moisture content.  What we find is that we get good = stabilization of the moisture level in the soundboard.  We = use relative humidity as a surrogate for moisture content in = wood.  Unfortunately they do not always directly correlate at any = given point in time.  The soundboard tends to equilibrate at constant = moisture content while relative humidity is cycling in a controllable, = repeatable cycle.  The equilibration of soundboard moisture content is the = driving force for all our product development research, and this is = reflected by the pitch stability which our product can provide to the = piano.  We discuss our product in terms of relative humidity, only because it is a concept that a layperson can easily grasp.</FONT></DIV> <DIV><FONT size=2></FONT> </DIV> <DIV><FONT size=2>I am one who believes in under promising and = over delivering.  I only recommend the hygrometer as a sales = tool.  I only claim the Climate Control System will help to provide = pitch stability.</FONT></DIV> <DIV><FONT size=2></FONT> </DIV> <DIV><FONT size=2>Maintenance of pitch stability is directly = dependent on how confined the space is in which the Climate Control System operates.  We have introduced a back side cover for = vertical pianos that provides better confinement.  We continue work on a = grand undercover to provide the same benefit.  We are pleased to have = received patents last year for both of these = systems.</FONT></DIV> <DIV><FONT size=2></FONT> </DIV> <DIV><FONT size=2>We also continue work on a better = Humidistat.  We experiment with electronic sensors that respond quickly to avoid the = "overshoot".  Unfortunately, the ones we have examined all = drift significantly.  (The electromechanical switch we now use does = not drift.) We cannot imagine a technician going in every year to = replace a sensor on a Humidistat.  We do monitor R&D on humidity = sensors and hope that the ideal unit will come along in the future.</FONT></DIV> <DIV><FONT size=2></FONT> </DIV> <DIV><FONT size=2>I would be happy to answer questions any of = you on the list might have if you would like to email me privately.  = We at Dampp-Chaser are genuinely thankful for your interest in our products and appreciate the diversity of opinions offered in = this forum.</FONT></DIV> <DIV> </DIV> <DIV><FONT size=2>Roger Wheelock<BR>Dampp-Chaser Corporation<BR><A = = href="mailto:roger@dampp-chaser.com">roger@dampp-chaser.com</A><BR><A = href="http://www.dampp-chaser.com">www.dampp-chaser.com</A><BR></FONT><= /DIV></BLOCKQUOTE></BLOCKQUOTE></BODY></HTML>